One should never forget Baltimore's Six Flags Power Plant.
Or maybe one should. It was an attempt by Six Flags to capitalize
on the early 1980's tourist boom in Baltimore's Inner Harbor; it came
too late to meet the boom, and it completely misjudged the nature of Baltimore
tourism.

Landmark USA still admits to having designed the Power Plant; the timeline
at their website
http://www.landmarkusa.com/company/default.asp?fl=0&pg=timelinelists some of the attractions:

The Magic Lantern Theatre

The Sensorium 4-D Experience

The Laboratory of Wonders

The Circus of the Mysterious

I went there once, right after it opened. The Sensorium was rather
interesting, a 3-D movie theater (it worked with polarized sunglasses)
whose seats moved and shook to simulate motion, and sprayed scents at
the viewers in the row behind. I don't recall a thing about the other
attractions, except that they were things you might want to experience once. I could see Phineas T. Barnum calling out "This Way
to the Egress!"

The Power Plant also featured a nightclub, P. T. Flagg's, which
lasted for about five years after the original museum closed. As
I recall, it gradually took over some of the space of the original Power
Plant. I recall secondhand; I never went there.

The Power Plant building was redeveloped in the later 1990's. It now
houses an ESPNZone (the first one), a Hard Rock Cafe, and an immense
Barnes and Noble bookstore. I've never been to any of those, either.

The Six Flags family is among the best-known theme parks in the United States. While Disney only has five flagship theme parks, Six Flags has twenty in the U.S. and one each in Canada and Mexico. Presently headquartered in New York City and Oklahoma City, the company has been running amusement parks for 45 years.

Six Flags got its start thanks to Angus Wynne, an oil tycoon from Texas who created Six Flags Over Texas in 1961. The park's name originated from the six flags that have flown over the state in its history - Spain, France, Mexico, the Republic of Texas, the Confederate States of America, and the United States of America. The park had six sections, each representing one of the cultures that had ruled Texas, and this was the first time someone had actually made a theme park, with specific theming as it is now known throughout the amusement industry.

The company's oldest park, Six Flags Over Texas, is located in Arlington, TX. Opening day, in August 1961, brought more than 8,000 visitors at the price of $2.75 per adult and $2.25 per child. In its first six weeks, the park attracted more than half a million visitors. Early attractions included a petting zoo, which was well-known for its baby elephant (there were actually several baby elephants, as each would be sold to a zoo when it got too old) until 1975 when the elephant died in the park. The petting zoo closed in 1982. SFOT had two scenic rides, the Astro-Lift cable car and the Six Flags Railroad. The latter is the only ride still operating from the original 1961 season, and the two trains are pulled by engine cars that were built in 1897 and 1901. The narrow-gauge railroad is considered an official railroad, and is regulated by the Texas Railroad Commission. Another still-operating early ride is the Silver Star Carousel, which made its debut in 1963. Built in 1925 by the Dentzel Carousel Company - which was bought by Philadelphia Toboggan Company two years later - the ride features 66 horses and two benches; its brass ring apparatus is no longer used and the organ is no longer present. The carousel was removed from the park in 1985 for restoration, and it returned in 1988. The park is also home to the original log flume ride, El Aserradero ("The Sawmill"), which has been operating since 1963. The park's first roller coaster was the Sidewinder, a steel wild mouse ride that closed in 1964.

The next park opened by the company, in 1967, was Six Flags Over Georgia. It was also split into themed sections based on the history of Georgia, including the state's confederate history, a replica mining town, and an area modeled after the 1895 World's Fair in Georgia. (These sections have mostly been rethemed to the standard Six Flags partnerships, including DC Comics and Looney Toons.) The Dahlonega Mine Train, a mine train type coaster, has been operating since the park opened; it was built by Arrow Development (now called Arrow Dynamics). Also open in the first season were a dark ride, a swinging ship, and a parachute-type ride by design firm Intamin. The park's popularity inspired the addition of new roller coasters, including the wooden Great American Scream Machine in 1973 and the steel Mind Bender, which was the first looping coaster in the south. The park's first kiddie coaster, a steel design also by Arrow, had opened in 1967; after it closed in 1988 (it was left standing until 1993, but didn't reopen during those five years) the park would not get another family coaster until 2004.

The next addition to what would become a major theme park empire was Six Flags Over Mid-America, which was renamed Six Flags St. Louis in 1997. It opened in 1971 at a cost of $50 million, and it would become the last park the Six Flags company built from scratch. The first roller coaster there was the River King Mine Train, another Arrow production. This was an example of a "twin" coaster, where there are two tracks that typically run side-by-side at the same time (many people refer to these as "racing" coasters). The two ran together from 1971 to 1988, when one of the tracks was removed and sold to the Dollywood amusement park; four years prior to that the trains had both been converted to stand-up cars, making the River King one of the earliest stand-up roller coasters. The park currently has seven coasters, the newest being Boss, a woodie installed in 2000.

After the construction of these three parks, Six Flags turned its focus toward purchasing existing parks. One of the first acquisitions was AstroWorld, a park near Houston that had opened in 1968, taking its name from the Houston Astro's - not-so-coincidentally owned by the same person who created the park. There were quite a number of themed areas, and the park offered typical "flat" rides such as teacups, a scrambler, dark ride, and ferris wheel. It was well-established, with multiple coasters, theatrical shows, and many rides by the time Six Flags bought it in 1975. AstroWorld's growth continued under the new ownership, and in 1983 the WaterWorld park opened adjacent to the dry park. The following year saw the first commercial tie-ins, as Six Flags Inc. licensed the Looney Tunes characters for use in the park. Rides came and went, and the park was rethemed, rehabilitated, and redesigned over the next 20 years. In 2005, Six Flags announced it would be closing the park at the end of the season; AstroWorld's last operating day was October 30, 2005.

The next park to join Six Flags was Great Adventure, in central New Jersey. Opened for the 1974 summer season, the park consisted of a 240-acre theme park, nicknamed the Enchanted Forest, and a 350-acre Safari area. To this day, the animal park is the largest drive-through safari outside of Africa. The first season's admission price was $7.50 for the theme park, $4.50 for the safari, or $9.50 for both. Bought by Six Flags in late 1977, the park would take many amusement "firsts" for the east coast. The 1978 addition of the Lightning Loops gave area residents their first experience with a looping coaster; the two interlocking loops were separate tracks (unlike the Loch Ness Monster at Busch Gardens Williamsburg), and when the coaster was removed in 1992 the tracks were sent to two different parks, dismantling the only example of Arrow's "launched loops." In 1980, the world's first massive swinging ship ride was installed at Great Adventure; today these are commonplace. The park's Great American Scream Machine, a steel coaster this time, opened in 1989 and was the world's tallest and fastest coaster for all of two weeks before Ohio's Cedar Point opened Magnum XL-200. In 1999, the world's first floorless coaster, the Bolliger & Mabillard-designed Medusa, opened at a cost of $15 million. Superman: Ultimate Flight, the first flying coaster, opened in 2003.

Many other famous parks have been added to the Six Flags family. Magic Mountain, a popular California park opened in 1971, was bought by Six Flags in 1979. In 1984, two more parks were purchased - Enchanted Village (opened 1977, and one of the few parks without "Six Flags" in the name) and Great America (opened 1976). Purchasing slowed for a few years, until the late 1990's when it picked up considerably. Wyandot Lake (also a non-branded park), originally opened in 1956, was purchased in 1995. Fiesta Texas was bought in 1996, and in 1998 four parks were purchased: Darien Lake (opened 1981), Six Flags America (opened 1982 as Wild World; operating as Adventure World when bought by Six Flags), Frontier City (opened 1958, no branding) and Kentucky Kingdom (opened 1987). More parks have been added nearly every year since then, including the first international Six Flags park, originally known as Flavohof and now called Six Flags Holland.